1. Technical Field
The present invention relates to a plasma processing apparatus for processing a semiconductor wafer or the like with plasma that is generated by microwaves or high frequency waves, and a method of cleaning the plasma processing apparatus.
2. Background Art
Plasma processing apparatuses for film formation, etching, and ashing have recently been used in the fabrication process of highly integrated semiconductor products. In particular, plasma processing apparatuses using microwaves or high frequency waves are frequently used because high density plasma can be stably generated even at a relatively low pressure (high vacuum state) of about 0.1 mTorr (13.3 mPa) to several 10 mTorr (several Pa).
Such plasma processing apparatuses are disclosed in Japanese Laid-Open Patent Publication No. hei 3-191073, Japanese Laid-Open Patent Publication No. hei 5-343334, Japanese Laid-Open Patent Publication No. hei 9-181052, Japanese Laid-Open Patent Publication No. 2000-3908, and Japanese Laid-Open Patent Publication No. 2003-332326. For example, a conventional plasma processing apparatus using microwaves will now be explained with reference to FIG. 5. FIG. 5 is a schematic view illustrating a configuration of a conventional plasma processing apparatus using microwaves.
Referring to FIG. 5, the conventional plasma processing apparatus 2 includes a holding stage 6 disposed in a process container 4 that can be vacuum evacuated, and allowing a semiconductor wafer W (hereinafter referred to as a wafer W) to be held thereon. A top plate 8 having a disk shape and formed of a microwave-transmissive material, such as aluminum nitride or quartz, is hermetically installed on the top of the process container 4 to face the holding stage 6. A shower head 9 for supplying a predetermined gas into the process container 4 is disposed in a sidewall of the process container 4.
A planar antenna member 10 that is disk-shaped and has a thickness of several millimeters (mm), and a wavelength-shortening member 12 formed of, for example, a dielectric material are installed over a top surface of the top plate 8. The wavelength-shortening member 12 is used to shorten the wavelength of microwaves in a radial direction of the planar antenna member 10. A plurality of slots 14, which are, for example, long and narrow through-holes, are formed in the planar antenna member 10. In general, the slots 14 are arranged in a concentric fashion or in a spiral fashion. A core conductor 18 of a coaxial waveguide 16 is connected to the center of the planar antenna member 10, so that microwaves having a frequency of, for example, 2.45 GHz generated by a microwave generator 20 are converted into a vibration mode by a mode converter 22, and then guided to the planar antenna member 10.
The microwaves guided to the planar antenna member 10 are propagated in the radial direction of the planar antenna member 10, radiated through the slots 14 formed in the planar antenna member 10, passed through the top plate 8, and supplied into the process container 4. Plasma is generated in a processing space S of the process container 4 by the microwaves, and predetermined plasma processing, such as etching or film formation, is performed on the wafer W using the plasma.